X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcMType.lhs;h=4a125364758d2ed2ca9b32efc2654ed4698d939c;hb=4e5faff9152918cd00dcdad9068b0f1eba1fcd68;hp=4aef89972372e62f0768e0b7ac801b97b6606ab8;hpb=a7ba22ff9bdc25d23af38ff1a2c9bbcc12dd45b8;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs
index 4aef899..4a12536 100644
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -49,7 +49,7 @@ module TcMType (
   zonkType, zonkTcPredType, 
   zonkTcTyVar, zonkTcTyVars, zonkTcTyVarsAndFV, zonkQuantifiedTyVar,
   zonkTcType, zonkTcTypes, zonkTcClassConstraints, zonkTcThetaType,
-  zonkTcKindToKind, zonkTcKind,
+  zonkTcKindToKind, zonkTcKind, zonkTopTyVar,
 
   readKindVar, writeKindVar
 
@@ -78,6 +78,7 @@ import Util
 import Maybes
 import ListSetOps
 import UniqSupply
+import SrcLoc
 import Outputable
 
 import Control.Monad	( when )
@@ -160,19 +161,30 @@ tcSkolSigTyVars :: SkolemInfo -> [TyVar] -> [TcTyVar]
 tcSkolSigTyVars info tyvars = [ mkSkolTyVar (tyVarName tv) (tyVarKind tv) info
 			      | tv <- tyvars ]
 
-tcInstSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
--- Instantiate a type with fresh skolem constants
-tcInstSkolType info ty = tcInstType (tcInstSkolTyVars info) ty
-
-tcInstSkolTyVar :: SkolemInfo -> TyVar -> TcM TcTyVar
-tcInstSkolTyVar info tyvar
+tcInstSkolTyVar :: SkolemInfo -> Maybe SrcLoc -> TyVar -> TcM TcTyVar
+-- Instantiate the tyvar, using 
+--	* the occ-name and kind of the supplied tyvar, 
+--	* the unique from the monad,
+--	* the location either from the tyvar (mb_loc = Nothing)
+--	  or from mb_loc (Just loc)
+tcInstSkolTyVar info mb_loc tyvar
   = do	{ uniq <- newUnique
-	; let name = setNameUnique (tyVarName tyvar) uniq
-	      kind = tyVarKind tyvar
-	; return (mkSkolTyVar name kind info) }
+	; let old_name = tyVarName tyvar
+	      kind     = tyVarKind tyvar
+	      loc      = mb_loc `orElse` getSrcLoc old_name
+	      new_name = mkInternalName uniq (nameOccName old_name) loc
+	; return (mkSkolTyVar new_name kind info) }
 
 tcInstSkolTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
-tcInstSkolTyVars info tyvars = mapM (tcInstSkolTyVar info) tyvars
+-- Get the location from the monad
+tcInstSkolTyVars info tyvars 
+  = do 	{ span <- getSrcSpanM
+	; mapM (tcInstSkolTyVar info (Just (srcSpanStart span))) tyvars }
+
+tcInstSkolType :: SkolemInfo -> TcType -> TcM ([TcTyVar], TcThetaType, TcType)
+-- Instantiate a type with fresh skolem constants
+-- Binding location comes from the monad
+tcInstSkolType info ty = tcInstType (tcInstSkolTyVars info) ty
 \end{code}
 
 
@@ -275,9 +287,14 @@ tcInstTyVars tyvars
 %************************************************************************
 
 \begin{code}
-tcInstSigTyVars :: SkolemInfo -> [TyVar] -> TcM [TcTyVar]
--- Instantiate with meta SigTvs
-tcInstSigTyVars skol_info tyvars 
+tcInstSigTyVars :: Bool -> SkolemInfo -> [TyVar] -> TcM [TcTyVar]
+-- Instantiate with skolems or meta SigTvs; depending on use_skols
+-- Always take location info from the supplied tyvars
+tcInstSigTyVars use_skols skol_info tyvars 
+  | use_skols
+  = mapM (tcInstSkolTyVar skol_info Nothing) tyvars
+
+  | otherwise
   = mapM (instMetaTyVar (SigTv skol_info)) tyvars
 
 zonkSigTyVar :: TcTyVar -> TcM TcTyVar
@@ -443,6 +460,30 @@ zonkTcPredType (EqPred t1 t2)
 		     are used at the end of type checking
 
 \begin{code}
+zonkTopTyVar :: TcTyVar -> TcM TcTyVar
+-- zonkTopTyVar is used, at the top level, on any un-instantiated meta type variables
+-- to default the kind of ? and ?? etc to *.  This is important to ensure that
+-- instance declarations match.  For example consider
+--	instance Show (a->b)
+--	foo x = show (\_ -> True)
+-- Then we'll get a constraint (Show (p ->q)) where p has argTypeKind (printed ??), 
+-- and that won't match the typeKind (*) in the instance decl.
+--
+-- Because we are at top level, no further constraints are going to affect these
+-- type variables, so it's time to do it by hand.  However we aren't ready
+-- to default them fully to () or whatever, because the type-class defaulting
+-- rules have yet to run.
+
+zonkTopTyVar tv
+  | k `eqKind` default_k = return tv
+  | otherwise
+  = do	{ tv' <- newFlexiTyVar default_k
+	; writeMetaTyVar tv (mkTyVarTy tv') 
+	; return tv' }
+  where
+    k = tyVarKind tv
+    default_k = defaultKind k
+
 zonkQuantifiedTyVar :: TcTyVar -> TcM TyVar
 -- zonkQuantifiedTyVar is applied to the a TcTyVar when quantifying over it.
 -- It might be a meta TyVar, in which case we freeze it into an ordinary TyVar.
@@ -662,7 +703,6 @@ checkValidType ctxt ty
 		 ConArgCtxt _   -> Rank 1	-- We are given the type of the entire
 						-- constructor, hence rank 1
 		 ForSigCtxt _	-> Rank 1
-		 RuleSigCtxt _	-> Rank 1
 		 SpecInstCtxt   -> Rank 1
 
 	actual_kind = typeKind ty
@@ -988,7 +1028,9 @@ even in a scope where b is in scope.
 
 \begin{code}
 checkFreeness forall_tyvars theta
-  = mappM_ complain (filter is_free theta)
+  = do	{ gla_exts <- doptM Opt_GlasgowExts
+	; if gla_exts then return ()	-- New!  Oct06
+	  else mappM_ complain (filter is_free theta) }
   where    
     is_free pred     =  not (isIPPred pred)
 		     && not (any bound_var (varSetElems (tyVarsOfPred pred)))
@@ -1111,7 +1153,8 @@ checkValidInstance tyvars theta clas inst_tys
 	  	  (instTypeErr (pprClassPred clas inst_tys) msg)
 	}
   where
-    msg  = parens (ptext SLIT("the Coverage Condition fails for one of the functional dependencies"))
+    msg  = parens (vcat [ptext SLIT("the Coverage Condition fails for one of the functional dependencies;"),
+			 undecidableMsg])
 \end{code}
 
 Termination test: each assertion in the context satisfies